In kidney dialysis treatment a connection must be made between the kidney dialyzer and the blood tubing set through which the patient's blood passes. This invention relates to a universal dialyzer end cap which provides a firm physical connection between the dialyzer and the blood tubing set while at the same time the patient's blood is not allowed to contact the inner surface of the end cap.
End caps are provided on the end of blood tubing sets for connecting the blood line to a nipple on an artificial kidney dialyzer. Prior art end caps are typically configured such that the end cap has an opening at one end for receiving the nipple and an opening at the other end into which the blood tubing line is permanently secured. However, the dimensions and fit are such that the end of the nipple does not actually extend into the blood line so that there is a gap between the end of the nipple and the blood line. Most end caps and blood tubing have been made of a material such as polyvinyl chloride (PVC) which contains a significant amount of plasticizers and lubricant. In addition PVC has certain thrombogenicity characteristics which make it undesirable for contact with blood. Because of the gap between the nipple and the tubing line in prior art end caps, blood flowing through the dialyzer contacts the PVC inner surface of the end cap and the PVC blood line. Because of the undesirable plastisizers and lubricant and the thrombogenicity characteristics of PVC this contact is highly undesirable.
One solution to this problem has been the introduction of blood tubing and end caps made of a polyurethane thermoplastic polymer sold by Renal Systems, Inc. under the trademark RENATHANE.RTM.. This urethane polymer is less thrombogenic than PVC and contains no plasticizers and little lubricant compared to PVC. Costwise, however, urethane is much more expensive than PVC.
The present invention offers another solution to the problem by providing a universal dialyzer end cap which is made of PVC but is configured such that the nipple of a kidney dialyzer when inserted in one end of the end cap is firmly force fit so as to extend into the blood tubing line. In this way the desirable mechanical properties of PVC provide a tight connection between the nipple of the dialyzer and the end cap on the blood tubing set while at the same time, blood flows through the nipple and directly into the blood tubing line. If a urethane blood tubing line or a line having at least a urethane inner lining is employed, blood never contacts the inner surface of the end cap which is PVC. Therefore the present invention provides an end cap which is safer and more biocompatible from the patient's standpoint. Another feature of the present invention is that the end cap opening that receives the nipple has a narrowing taper to conform more closely to the nipple. As the end cap is pushed into the nipple the PVC expands to cause a tight grip. This action coupled with the expansion of the urethane tubing line, caused by entry into the tubing line of the nipple creates a banding effect to make the grip of the urethane tubing line on the nipple even greater. Another advantage of the present invention is that the opening which receives the dialyzer nipple, has a 30.degree. chamfer to facilitate entry. The end cap of the present invention is provided with a closure such that gases are allowed to the interior of the tubing set to achieve adequate sterilization by well known sterilization processes utilizing ethylene oxide as the sterilizing agent. The closure maintains the interior of the tubing set clean before, during and after sterilization. Sterility is maintained by using appropriate packaging, such as a gas-permeable tubing set pouch that is impermeable to bacteria.